The present invention relates to combustors for large combustion turbines and more particularly to combustors capable of satisfying emission and combustion performance requirements while burning fuel which carries particulate matter.
To achieve decreased dependence on oil as a fuel, it is desirable to develop a combustion turbine capability for burning pulverized coal which is often low in sulfur content as a result of the manner in which it is produced. While providing for the burning of pulverized coal, there is a simultaneous need to provide any new combustor with operating characteristics which meet both turbine combustion performance specifications and exhaust emission requirements.
As compared to the burning of coal in conventional boilers, special problems are encountered in burning pulverized coal in a combustion turbine since the combustion products are passed through the turbine blade path. Particulate matter in the combustion products can damage the vanes and blades through erosion and deposition and/or shorten the turbine operating life. Some protection can be provided against particulate carry-over by a ruggedized turbine design but this is an expensive alternative with limited effectiveness. Similarly, the use of cleaning devices between the combustor and the expander is costly, structurally cumbersome and limited in effectiveness.
One recent basic development in the combustor art is a multi-annular swirl (MAS) burner. The MAS burner operates with respective rich and lean combustion zones where combustion vortices and recuperative cooling occur. The MAS burner provides efficient combustion for efficient turbine operation and is especially valuable in producing turbine operation reduced nitrogen oxide emissions. Reference is made to a copending application Ser. No. 488,145, entitled "Gas Turbine Combustor" filed by Janos M. Beer on May 25, 1982, now abandoned, and filed as a continuation application Ser. No. 661,264, filed Oct. 15, 1984, for more details on the MAS burner.
The present invention is directed to an improvement in the MAS combustor to provide a combustor capable of burning particulate carrying fuels like pulverized coal slurry, while satisfying turbine performance and exhaust emission requirements.